Fabrication of a Luminescent Supramolecular Hydrogel Based on the AIE Strategy of Gold Nanoclusters and their Application as a Luminescence Switch
Junxiao Liu, Feng Jin, You Yu, Liandi Xu, Qi Liu, Hao Zhang, Jinglin Shen, Wei Qi
Abstract
Gold nanoclusters (AuNCs) have been recognized as an emerging category of inorganic–organic hybrid luminescent materials owing to their ultrasmall size, good biocompatibility, and especially the aggregation-induced emission (AIE) property. Some works have been reported about the AIE property of AuNCs; however, the mechanism is still indistinct. In the present work, we studied the coassembly behavior of thiobarbituric acid-modified AuNCs (TBA-AuNCs) with Zn2+. The coassembly system could not only enhance the emission of AuNCs but also induce the gelation along with the morphology transformation from nanofibers to micron-sized bowknot-like aggregates. Various methods were used to characterize the properties of a hydrogel such as photoluminescent (PL) spectra, morphology, lifetime, and intermolecular interaction. Significantly, time-/temperature-dependent PL spectra as well as morphological evolution monitoring were implemented to analyze the structure–emission property relationship of TBA-AuNCs assembly systems. It is verified that the π–π stacking of ligands, ligand-to-metal charge transition (LMCT), and the orderliness degree of aggregates contribute uniquely to the emission energy/intensity of TBA-AuNCs, which is significant for the comprehension of the AIE nature of nanoclusters. Besides, the gelation and photoluminescence of TBA-AuNCs are sensitive to heating and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), making the hydrogels promising candidates as smart luminescent switches. This work is of interest for not only providing a versatile methodology for lighting up AuNCs through gelation but also pointing out a way to understand and regulate the emission of AuNCs.